The proposed research is directed to a central theme involving study of the effects of changes in pressure on the respiratory and circulatory processes by health related physicians and scientists. The research is designed to assist in maintaining the health and safety of individuals required to work under conditions of altered pressure and to elucidate mechanisms of respiratory and circulatory function using pressure as the probe to acquire information which may help in understanding the prognosis and treatment of illness related to the lung and heart. Primarily this involves study of the effects of exposure to hypo-or hyperbaric environments under a number of categories: 1. The effects of increased pressure, gas density, and narcosis on the regulatory mechanisms of respiration, circulation and performance efficiency. 2. Studies of the morphological and metabolic effects of pulmonary oxygen toxicity. 3. Non-invasive measurements of intracellular oxidation and oxidative energy metabolism. 4. High altitude hypoxia. 5. Detection and measurement of gaseous emboli in the circulation and their induced blood damage.